1. Field of the Invention
This invention relates to an inspecting apparatus and method for a foreign matter (impurities) that enable inspection of all products to detect a foreign matter contained in liquid products (including fluid products) such as beverages and chemicals without stopping a high-speed mass production line, and particularly to an inspecting apparatus and method for a foreign matter that enable secure detection of even a very small foreign matter contained in a liquid product in a container as an inspection subject without making any misjudgment, with the container having a recessed and protruding shape on its lateral side such as a cylindrical container like a PET (polyethylene terephthalate) bottle or a rectangular container like a rectangular bottle and containing a liquid product.
2. Background of the Invention
Recently, as HACCP (Hazard Analysis Critical Control Point System) has been applied to the Food Safety Law and the Product Liability Law has been enforced, it is becoming an obligation to prevent accidents such as microbe contamination that might occur at any stage of manufacturing/processing of products such as foods and chemicals and preservation/circulation of the products before end consumers take them, and contamination by metal, cloth, hair and the like, and to achieve further security of the products.
HACCP is a hazard analysis critical control point system of the United States, which is internationally appreciated as a sanitation control system. This HACCP system is a scientific sanitation control system to achieve safety of products throughout manufacturing processes. Contrary to the conventional sanitation control system, which emphasizes inspection of end products, the HACCP system emphasizes preventive measures in manufacturing processes. The HACCP system consists of two parts, that is, hazard analysis (HA) and critical control point (CCP). The hazard of microbe contamination or the like that might occur at any stage of manufacturing/processing of foods and preservation/circulation of the products before end consumers take them is examined and analyzed, and critical control points for hazard prevention are set. At the same time, control standards are defined so as to check control records to constantly monitor whether appropriate measures are taken within the standards. For other types of hazards, administration and control are based on general sanitation control standards (PP or prerequisite program). Thus, any occurrence of hazard in manufacturing processes is prevented without oversight and further security of products is achieved.
Conventionally, in a mass production line at a manufacturing plant, visual inspection by workers or the like is carried out to detect a foreign matter contained in a liquid after filling a container with it. Since such visual inspection takes time and labor, sampling inspection to select one of every given number of containers for inspection is carried out. Therefore, there is a problem that this is not a secure inspection technique for all the products.
In a complete inspection system where inspectors are stationed in the production line, though relatively large foreign matters can be detected by visual judgment by the workers, there is a problem that very small foreign matters cannot be detected, resulting in low detection accuracy. Moreover, practically, the visual judgment capability of the inspectors cannot catch up with the increasingly higher speed of the production line, resulting in low inspection efficiency.
As a technique for detecting a foreign matter contained in a container after it is filled with a liquid without using visual inspection, a technique of photographing a container from outside by an inspection camera and then detecting the existence of any defect based on the acquired image information is considered.
FIG. 1 shows one example of this. A container 101 moving without having any spacing into the direction of an arrow X on a production line is used as an inspection subject. The container 101 is illuminated from its lateral side by a light source 100. Transmitted light from the container 101 is received by a CCD sensor 102, which is an image pickup unit. A light-receiving signal from the CCD sensor 102 is image-processed by a data processing device (not shown). A foreign matter contained in a liquid product in the container 101 (foreign matter 103 in FIG. 1 or the like) is thus detected. In such an inspecting apparatus, the CCD sensor 102 receives the transmitted light from the container 101 and the light-receiving signal from the CCD sensor 102 is processed by an image processing device such as a personal computer. A foreign matter contained in the liquid product in the container 101 is thus detected (see, for example, Patent Reference 1).
Patent Reference 1: JP-A-2001-221746
Patent Reference 2: JP-A-2003-315280
In the inspecting apparatus as described above, there is no problem with a container having a simple shape and having no recess and protrusion on its surface. However, in the case of a container having a recessed and protruding shape on its lateral side such as a rectangular bottle or PET bottle, the recessed and protruding shape appears on its picked-up image, making it difficult to detect a foreign matter. That is, since reflection on the container surface of scattered light from outside and problems on the emission line are caused by the diverse and complicated container shapes and materials, the recess and protrusion on the container surface and the contour of the container cause changes in luminance similar to those caused by foreign matters and image information (raw data) as shown in FIG. 2 is acquired by the CCD sensor 102. Therefore, even when the image information is processed by the image processing device and a binary image as shown in FIG. 3 is acquired, it is difficult to accurately discriminate only a foreign matter on the image. In short, in addition to lowering of reliability, there is a problem of deterioration in manufacturing yield because a foreign matter and an irregular reflection part of the container cannot be discriminated from each other, resulting in detection error.
In consideration of the above-described problems, which occur when a container having a recessed and protruding shape is used as a subject, for example, an inspecting apparatus for foreign matter disclosed in Patent Reference 2 by the present applicant is provided. For example, when this inspecting apparatus for foreign matter is applied to a production line, light is cast onto an inspection subject 101, which is a container moving on the production line into the direction of an arrow X and contains a liquid product, from a first lateral side by a light source 100A, and light is cast onto the inspection subject 101 by two light sources 100B, 100C from two inclined directions on a second lateral side opposite to the first lateral side (at an inclination angle of 30 to 60 degrees to a perpendicular line to the subject inspection on the first lateral side), as shown in FIG. 4. Then, an image pickup unit (CCD sensor) 102 near the second lateral side receives transmitted light and reflected light from the inspection subject 101. On the basis of an image signal from the image pickup unit 102, a foreign matter contained in the liquid product (foreign matter 103 in FIG. 4 or the like) is detected (see Patent Reference 2).
In such an inspection technique, the outer shape line of the inspection subject 101 (PET bottle or the like) is eliminated from the image captured by the image pickup unit 102, thus enabling highly accurate detection of a foreign matter contained in the liquid product. However, in the case of the optical inspection for a foreign matter on a straight line as in the inspecting apparatus described in Patent Reference 2, there is a problem that a blind spot is generated when light is transmitted. If a recessed and protruding shape exists or a foreign matter exists in the blind spot, it is difficult to discriminate the foreign matter from the recessed and protruding part, and a misjudgment may occur. For example, in the arrangement of the optical system as shown in FIG. 4, if the inclination angle is 45 degrees and a PET bottle having large recesses and protrusions is a subject, the CCD sensor 102 may acquire image information (raw data) as shown in FIG. 5, depending on the direction of the PET bottle. Therefore, even when the image information is processed by the image processing device to acquire a binary image as shown in FIG. 3, a part of the recesses and protrusions of the container and the contour of the container cannot be totally optically eliminated, and in some cases, it is not possible to accurately discriminate only the foreign matter on the image. Also, in the optical inspection for a foreign matter on a straight line as in the inspecting apparatuses described in Patent Reference 1 and Patent Reference 2, even when the arrangement of the optical system is advantageously contrived, the linear carrier path may become a barrier. When inspecting the container 101 carried along with the other containers in a chained manner as shown in FIG. 1, the adjacent containers may become obstacles. Therefore, it is not possible to completely eliminate the blind spot.
As another inspection technique, a technique of performing image editing based on software after capturing an image and thus masking unwanted parts outside of the inspection area such as the shape line of the container may be considered. However, usually, products with various rotation angles move into the image pickup area of the inspecting apparatus installed on the production line. Therefore, when images of the containers are captured, the position of the recess and protrusion on the surface of the container differs each time, thus causing a problem that it is impossible to fixedly set the masking area.